<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        #main{
            width:1000px;
            margin:auto;
        }
        #smallpic{
            height:120px; 
        }
        img{
            float:left; 
            margin-right:10px; 
            margin-bottom:10px;
        }
        #smallpic img:hover{
            cursor:pointer;
        }
        .pb {
            border:3px solid red;
        }
    </style>
</head>
<body>
    <div id="main">
        <div id="smallpic">     
            <img src="images/1.jpg" class="test" width="180" height="100" />
            <img src="images/2.jpg" class="test" width="180" height="100"/>
            <img src="images/3.jpg" class="test" width="180" height="100"/>
            <img src="images/4.jpg" class="test" width="180" height="100"/>
            <img src="images/5.jpg" class="test" width="180" height="100"/>
        </div>
        <div>
            <img src="images/0.jpg" id="bigpic"/></div>
        </div>
</body>
<script>
    var smallpic = document.getElementById("smallpic");
    var imgList = document.getElementsByTagName("img");
    var bigpic = document.getElementById("bigpic");
    for(var i = 0;i<imgList.length;i++){
        imgList[i].onclick = function(){
            for(var j = 0;j<imgList.length;j++){
                // if(imgList[j].hasAttribute("class")){
                //     imgList[j].removeAttribute("class");
                // }
                var classStr = imgList[j].getAttribute("class");
                var classArr = classStr.split(" ");
                if(classArr.indexOf("pb")>=0){
                    var index = classArr.indexOf("pb");
                    classArr.splice(index,1);
                    var str = classArr.join(" ");
                    imgList[j].setAttribute("class",str);
                }
                else{
                    continue;
                }
            }
            this.setAttribute("class","pb");
            var imgSrc = this.getAttribute("src");
            bigpic.setAttribute("src",imgSrc);
        }
    }
</script>
</html>